JP2017516081A - Ceramic carrier, sensor element having ceramic carrier, heating element and sensor module, and method for producing ceramic carrier - Google Patents

Abstract

The present invention relates to a ceramic support, in particular an Al2O3 support, on which a platinum or platinum alloy thin film structure (10) is arranged. The carrier and / or thin film structure is adapted to reduce mechanical stress due to different coefficients of thermal expansion. The carrier and / or thin film structure (10) has the following characteristics. (E) In order to reduce adhesion, in the region of the thin film structure (10), the surface (11) of the carrier is at least partially smoothed and / or (f) the surface (11) of the carrier is intermediate layer (12), on which the thin film structure (10) is arranged, and the thermal expansion coefficient of the intermediate layer (12) is 8 × 10 −6 / K to 16 × 10 −6 / K, in particular 8.5 × 10 −6 / K to 14 × 10 −6 / K and / or (g) the thin film structure (10) has at least one conductor path (13) that is at least partially wavy. The conductor track extends along the surface (11) of the carrier, and the amplitude of the wavelike conductor track (13) is 0.2 × B to 2 × B, in particular 0.4 ×. B to 1 × B and the wavelength of the wavy conductor track (13) is 3 × B to 10 × B, in particular 4 × B to 7 × B, where “B” The width of the channel (13) and / or (h) a first coating (14a) is applied directly to the thin film structure (10), which coating is made of oxide nanoparticles, in particular Al 2 O 3 and / or Or MgO nanoparticles.

Description

The invention relates to a ceramic support, in particular an Al ₂ O ₃ support, having the features of the preamble of claim 1.

  This type of carrier is known, for example, from JP 59-065216. The carrier is coated with a thin film structure made of platinum and used as a flow sensor for flow measurement.

  Sensors of the same design principle are used as temperature measuring sensors in the exhaust gas sensor system. These are installed upstream of the diesel soot filter to detect the temperature of the exhaust gas, for example for regeneration of the filter. In this regard, platinum thin film sensors are exposed to severe fluctuating temperature loads. This needs to be taken into account when designing the sensor with the intended service life required in the automotive industry. The same is true in the automotive industry when using platinum thin film sensors to monitor the condition of engine oil (its tribological properties are highly dependent on heating). In order to determine the condition of engine oil, the total heat load is an important measurement variable identified by the platinum temperature sensor. In this regard, the sensor is subject to many temperature change cycles, severe vibration loads, and corrosion by the measurement medium.

  The electrical resistance of a platinum sensor changes in a strictly defined manner with respect to temperature. Therefore, avoiding measurement errors depends on suppressing as much as possible other influence variables that change the electric resistance. This problem arises when different materials are paired when there is a severe fluctuating temperature load. This is the case, for example, with ceramic supports having a platinum thin film structure. These different materials have different coefficients of thermal expansion. This is also called a mismatch. In the presence of variable temperature loads, the plastic structure of the platinum structure occurs due to the different thermal properties of these materials, and dislocation migration occurs in the microstructure. As a result, the material properties change. This leads to resistance drift, i.e. undesirable mechanically induced resistance value fluctuations. If the mechanical stress in the platinum thin film structure is severe, the latter can also be damaged or suspended.

In the past, attempts have been made to address this problem by combining materials with similar coefficients of thermal expansion. For example, a ceramic support made of zirconium oxide is used in combination with a platinum thin film structure. However, they have the following drawbacks. The element so constructed, when further mechanically placed on an Al ₂ O ₃ ceramic hybrid carrier or module, cracks and eventually breaks upon cooling as a result of the higher level of expansion.

  In the prior art cited in the introduction, another method is performed. It is an attempt to reduce heat-induced stress by using a glass layer between the support and the platinum film. Sensors having such a structure do not meet the high demands regarding the stability and durability of thin film sensors in the automotive industry.

  An object of the present invention is a ceramic carrier on which a thin film structure made of platinum or a platinum alloy is arranged, and the ceramic having an improved resistance value drift when there is a high fluctuating temperature load. It is to identify the carrier. A further object of the present invention is to identify a sensor element, a heating element and a sensor module comprising such a carrier and a method for producing such a ceramic carrier.

  According to the invention, the object relating to the ceramic carrier is achieved by the subject matter of claim 1, the object relating to the sensor element, the heating element and the sensor module is achieved by the subject matter of claim 16, and the object relating to the method is claimed in claim. Achieved by 18 themes.

The invention includes as a specification a ceramic support, in particular an Al ₂ O ₃ support, on which a thin film structure made of platinum or a platinum alloy is arranged. The carrier and / or thin film structure is adapted to reduce mechanical stress due to different coefficients of thermal expansion. This is achieved according to the invention by the following features of the carrier which, when viewed individually, each reduce resistance drift. This effect is enhanced by combining these features.

  The features specified below each implement the basic concept of reducing or mitigating mechanical stresses in the thin film structure due to different thermal expansion coefficients between the support and the thin film structure. For this purpose, the relative movement between the carrier and the thin film structure is at least partly allowed and / or the improvement of the thin film structure compensates for differences in material expansion caused by heat. Thereby, the mechanical stress caused in the thin film structure is made as low as possible.

  Specifically, according to the invention, this is achieved by at least partially smoothing the carrier surface in the region of the thin film structure in order to reduce adhesion (feature a).

  The effect of reducing the roughness reduces the degree of adhesion of the thin film structure to the support surface, thereby allowing relative movement between the support and the thin film structure. The mechanical separation thus achieved reduces the risk of plastic deformation of the thin film structure due to the thermal expansion difference between the carrier and the thin film structure.

In addition or alternatively, the surface of the carrier has an intermediate layer on which the thin film structure is arranged. Thermal expansion coefficient of the intermediate layer is ^{8 × 10 -6 / K~16 × 10} -6 / K, in particular ^{8.5 × 10 -6 / K~14 × 10} -6 / K ( wherein b).

  By setting the thermal expansion coefficient of the intermediate layer within the above range, even in the case of frequent temperature change cycles, an optimum bond between the ceramic support and the platinum thin film structure that does not lead to large deformation of the platinum thin film structure is achieved. It turns out that it can be achieved. Thus, the intermediate layer becomes an effective transition from the carrier to the platinum thin film structure, which acts as a buffer and absorbs some of the mechanical stress.

  In addition or alternatively, the thin film structure has at least one conductor track, which is at least partly corrugated and extends horizontally along the surface of the carrier (feature c). The waveform of the conductor track extends in a plane parallel to the surface of the carrier. The corrugations are thus formed in the horizontal direction, i.e. in the surface of the carrier, not in the depth direction. The corrugations can extend in one and the same plane parallel to the surface of the carrier. This is the case when there is no profile on the surface of the carrier, i.e. the surface is continuously flat. Further, a further waveform in the depth direction of the carrier can be superimposed on the waveform in the horizontal direction. For example, this is brought about by a combination with a profile in the depth direction, which will be further described below. The main orientation of the waveform is in the horizontal direction.

  The amplitude of the corrugated conductor path is 0.2 × B to 2 × B, particularly 0.4 × B to 1 × B. The wavelength of the corrugated conductor track is 3 × B to 10 × B, in particular 4 × B to 7 × B, where “B” is the width of the conductor track in each case.

  Thanks to this shape, the corrugated conductor path relieves the mechanical stress produced in the thin film structure due to the expansion difference between the carrier and the thin film structure. Overall, corrugated conductor paths, in contrast to linear or non-corrugated conductor paths, result in less deformation. The stress concentration in the conductor path can be changed in a desired manner depending on the waveform shape.

In addition or alternatively, a first coating layer comprising oxide nanoparticles, in particular oxide nanoparticles consisting of Al ₂ O ₃ and / or MgO, is applied to the thin film structure (feature d).

  The first coating layer forms a passivation layer to protect the platinum thin film structure. When there is a temperature change, the oxide nanoparticles change the volume of the coating layer in accordance with the expansion of the platinum thin film structure.

  It has been found that the resistance value drift is effectively reduced by combining the features a, b, c and d as follows. Other combinations of features obtained from claim 1 are not excluded.

In each case, a combination of feature d and one of features a, b and c.
A combination of features a, c and d.
A combination of features b, c and d.
A combination of features a, b, c and d.

  In a preferred embodiment of the invention, the surface in the region of the thin film structure forms at least one sliding part and at least one tight contact part. The surface roughness of the carrier is higher in the close contact area than in the sliding area. In other words, the sliding part is smoothed. The close contact portion is not smoothed or is less smoothed than the sliding portion.

  This is an advantage, that is, good adhesion of the untreated surface is maintained in an unimportant region (contact portion) of the thin film structure, and in a desired manner in a region (sliding portion) where a large stress occurs in the case of a temperature change. There is an advantage that adhesion is reduced. In extreme cases, relative movement occurs between the surface of the carrier and the thin film structure in the region of the sliding part. The thin film structure remains bonded to the surface of the carrier in the region of the one or more close contact portions. As a result, the thin film structure is fixed to the carrier at a predetermined portion and is separated from the carrier at the predetermined portion, thereby enabling relative movement between the surface of the carrier and the thin film structure.

  On the other hand, the surface can be smoothed in the entire region of the thin film structure. This modification has the advantage that it is easy to manufacture. The thin film structure is sufficiently fixed. This is because, due to the non-uniform temperature distribution that typically occurs during operation, local heat-induced stresses occur, and portions of the thin film structure are exposed to different levels of load.

  In a preferred embodiment, the surface in the region of the thin film structure has a profile in the depth direction that forms at least one recess, particularly in the shape of a band, and the surface of the recess is smoothed. The surface of the recess is less rough than a region at a higher position in the depth profile (for example, an unprofiled surface region of the carrier).

  This has the effect that the thin film structure can be detached from the recess during expansion. In this case, the thin film structure is partly mechanically separated from the carrier. In addition, the thin film structure can be stretched in the region of the recess when detached, thereby changing its shape and consequently reducing the mechanical stress in the thin film structure.

  In a preferred embodiment, the at least one conductor track of the thin-film structure is arranged at an angle in particular in the range of 30 ° to 90 ° with respect to the strip-like profile in the depth direction. This embodiment provides effective compensation of expansion for common conductor track structures. In the case of meandering conductor tracks, they repeatedly traverse the strip-like profile in the depth direction, so that expansion compensation is performed at a plurality of locations on the conductor tracks. This also applies to carriers having a plurality of individual conductor tracks.

  The recess may have a trapezoidal cross section having two inclined side surfaces and a bottom surface between the side surfaces. These two side surfaces determine the boundary of the bottom surface of the recess in the horizontal direction. At least one side, in particular both sides, rises at an angle of 10 ° to 80 °, in particular 45 ° to 60 ° with respect to the bottom. This angle is measured between a virtual surface that spans the bottom surface and another virtual surface that defines the target side surface. This embodiment has an advantage that the thin film structure can be easily detached from the recess. This is because the wall or side surface of the recess is inclined. The side surface and the bottom surface of the recess are preferably smoothed. This further facilitates detachment.

  The depth of the recess is preferably 0.4 μm to 1.2 μm, particularly preferably 0.6 μm to 1.0 μm, and / or the width of the recess is preferably 5 μm to 20 μm, particularly preferably 10 μm to 15 μm. The dimensions of the recesses are selected depending on, among other things, the thickness of each layer of the structure.

  The strip-like profile in the depth direction can have a plurality of parallel recesses, and the interval between the recesses is 5 μm to 20 μm, particularly 10 μm to 15 μm. An individual conductor track or a plurality of conductor tracks intersect a plurality of parallel recesses, so that expansion compensation is repeated along the length of one or more conductor tracks. This provides the advantage that resistance drift is reduced along the entire conductor track and / or in a particularly important part of the conductor track.

  In a preferred embodiment, the thermal expansion coefficient of the intermediate layer is up to 1.5 times the thermal expansion coefficient of the thin film structure. In order to optimize the buffering action of the intermediate layer, it has proved advantageous to limit the upper limit of the thermal expansion coefficient of the intermediate layer.

  The thickness of the intermediate layer can be 0.2 μm to 3 μm, in particular 1 μm to 2.2 μm. These thicknesses have proven to be advantageous in practice.

  The intermediate layer may include at least one electrically insulating metal oxide. In particular, the entire intermediate layer may be made of an electrically insulating metal oxide. Since the metal oxide is electrically insulated, successive regions of the support can be covered with the metal oxide as an intermediate layer without thereby compromising the function of the platinum thin film structure.

In particularly preferred embodiments, the intermediate layer comprises MgO and / or BaO. The entire intermediate layer may consist of MgO and / or BaO and inevitable impurities. As an alternative, the intermediate layer may comprise or consist entirely of a mixture of at least one electrically insulating metal oxide and Al ₂ O ₃ . The metal oxide of this mixture can be MgO and / or BaO. The advantage of the mixture with Al ₂ O ₃ is that the thermal expansion coefficient of the intermediate layer can be changed by setting the content of Al ₂ O ₃ , and thereby the combination of each material of the support and the thin film structure Accordingly, the thermal expansion coefficient of the intermediate layer may be optimized depending on the thermal and mechanical requirements.

  In a further preferred embodiment, the corrugated conductor track has a plurality of arcs extending horizontally along the surface, and a corrugated structure is formed at least in the conductor track portion between the arcs. Alternatively, the corrugated conductor path may form a plurality of electrode fingers arranged in a comb shape.

  For example, in the case of a general sensor element for temperature measurement, the arrangement of the conductor path has a meandering structure. The meandering shape of the conductor path constitutes the superstructure. The corrugations of the conductor tracks form the lower structure, which is integrated into the upper structure and extends along the portion of the conductor path between the arcs of the upper structure. The formation of the substructure and its effect on resistance drift is substantially independent of the formation of the superstructure. In this regard, the term “arc” should be understood broadly and can encompass curvilinear or rectangular changes in direction in the conductor track.

  The corrugated conductor path may be implemented in the form of a sine wave and / or a sawtooth wave and / or a trapezoidal wave. Different shapes of the waves affect the stress concentration distribution in the conductor track when the thermal load varies. The shape is selected in consideration of the respective conditions of use of the carrier.

  The first covering layer may be hermetically sealed with a second covering layer made of glass in particular. As a result, the first covering layer or the entire platinum thin film structure is reliably protected from corrosion by the measuring medium.

  The carrier is integrated into the sensor element or heating element or sensor module. Possible sensor elements are, for example, temperature sensor elements, flow sensors, soot sensors and the like. The carrier according to the invention may be a component of a heating element. The sensor module is a basic module with a multi-functional structure and based on platinum thin film technology. These consist, for example, of sensor / heater combinations and electrodes configured in a manner specific to the application. A sensing layer may be applied to the electrode by the customer.

  In a preferred embodiment of the sensor module, various sensor structures are placed on the carrier. In this regard, the thin film structure made of platinum or platinum alloy may form at least one sensor structure, and the electrode structure may form at least one other sensor structure. In particular, the platinum thin film structure can form a temperature sensor / heater combination.

  The method for producing a ceramic carrier according to claim 1 comprises removing and smoothing at least the surface of the carrier in the region of the thin film structure by etching, in particular plasma ion etching. In addition or alternatively, the intermediate layer may be applied to the surface of the support by thin film methods, in particular PVD methods or CVD methods. In addition or alternatively, corrugated conductor tracks may be applied to the surface of the carrier by thin film methods, in particular PVD or CVD methods or lithographic methods.

  The invention will be described in more detail below on the basis of exemplary embodiments and with reference to the accompanying drawings. A brief description of the drawings follows.

1 is a cross-sectional view of a carrier according to an embodiment of the invention, the surface of which is configured with a depth profile. FIG. 2 is a cross-sectional view of a carrier according to another embodiment of the present invention, the surface of which is configured as in FIG. It is a top view of the support | carrier shown in FIG. FIG. 6 is a cross-sectional view of a carrier according to another embodiment of the present invention in which an intermediate layer is disposed between the platinum thin film structure and the carrier. It is a top view of the corrugated conductor path compared with the linear conductor path. a to d are plan views of corrugated conductor paths having different shapes. FIG. 4 is a cross-sectional view of a carrier according to another embodiment of the present invention in which a platinum thin film structure is protected with a coating layer. 2 is an exploded view of a sensor module comprising various thin film structures disposed on a carrier according to an embodiment of the present invention. FIG.

FIG. 1 is a cross-sectional view of a ceramic carrier according to an embodiment of the present invention. Specifically, this ceramic support is an Al ₂ O ₃ support (aluminum oxide support). This carrier serves as a substrate or ceramic support for the thin film structure (not shown in FIG. 1). Al ₂ O ₃ has been found to be advantageous as a material for the ceramic support, particularly a ceramic support with an Al ₂ O ₃ content of 96 wt% or more, and a ceramic with an Al ₂ O ₃ content of 99 wt% or more. A carrier is more preferred. The carrier can be in the form of a plate having a thickness in the range of 100 μm to 1000 μm, in particular in the range of 150 μm to 650 μm. Other plate thicknesses are possible. In view of the behavior of thermal response, it is desirable to select the thickness of the carrier as thin as possible. Particularly in applications in the automotive field, severe vibration loads frequently occur, so the lower limit of the plate thickness is determined by the mechanical stability of the carrier. The ceramic carrier can be a rectangular plate. Other shapes for the carrier are possible.

  The above description regarding the general shape of the carrier and the composition of the material generally applies to the present invention and is disclosed for all embodiments.

  The carrier shown in FIG. 1 is designed to reduce mechanical stress due to the difference in thermal expansion coefficient of the material used. For this purpose, the surface of the carrier in the region of the thin film structure is smoothed. There are two possible ways for this purpose. One is to smooth the carrier in the entire region of the thin film structure. This is easy to realize from a manufacturing point of view. Another is to partially smooth the carrier in the region of the thin film structure.

  The smoothed surface 11 has the effect that the adhesion of the thin film structure is reduced, so that the thin film structure with reduced adhesion is placed on the surface 11 of the carrier in order to compensate for the difference in linear expansion. Can slide. If the surface 11 is partially smoothed only in critical areas, the untreated surface area ensures tight adhesion to the thin film structure. An example is shown in FIG. The surface 11 has a strip-like profile in the depth direction that forms at least one recess 17, and the surface 11 of the recess 17 is smoothed. The areas of the surface 11 on both sides directly adjacent to the recess 17 are not treated. As a result, the surface 11 of the carrier forms a sliding portion 15 in the region of the recess 17, and in any case, the horizontal boundary of the sliding portion is determined by the contact portion 16. The close contact portion 16 is formed by a surface region adjacent to the concave portion 17.

  In the region of the sliding portion 15 or the concave portion 17, the adhesion between the platinum thin film structure shown in FIG. 2 and the carrier is reduced. If the platinum thin film structure 10 is linearly expanded, this can result in the thin film structure being detached in the region of the recess 17. Since these surface areas of the carrier adjacent to the recesses 17 have not been treated, the roughness in these areas is higher than the area of the recesses 17. The close contact portion 16 thus formed fixes the platinum thin film structure 10 between the sliding portions 15 or the recesses 17. When the platinum thin film structure linearly expands, the thin film structure can leave the region of the recess 17 and be stretched. Such a change in the shape of the platinum thin film structure 10 is coupled with the separation from the carrier, and the effect of remarkably preventing the deformation of the platinum thin film structure 10 due to the difference in thermal expansion coefficient between the carrier and the platinum thin film structure 10. Have

  Removal of the platinum thin film structure 10 from the surface 11 is facilitated by the fact that the recess 17 has a trapezoidal cross section. The cross section is defined by two side surfaces 18. The two side surfaces 18 are inclined and determine the horizontal boundary of the bottom surface 19 of the recess 17. The side surface 18 rises at an angle of 10 ° to 80 °, particularly 45 ° to 60 °. This angle is determined by the first virtual plane passing through the bottom surface 19 and the second virtual plane passing through the target side surface. The depth of the recess 17 can be in the range of 0.4 μm to 1.2 μm, particularly in the range of 0.6 μm to 1.0 μm. Its width can be 5 μm to 20 μm, in particular 10 μm to 15 μm.

  As can also be seen in FIG. 1, the strip-like depth profile has a plurality of parallel recesses 17 extending along the surface 11 of the carrier. The space | interval of the recessed part 17 can be 5 micrometers-20 micrometers, especially 10 micrometers-15 micrometers. The recesses 17 are arranged in parallel at equal intervals.

  Instead of a partially smoothed surface resulting from the formation of a depth profile, the surface can be smoothed without a profile. This means that the surface is evenly smoothed without a profile in the depth direction.

  Smoothing can be done by removing the surface. This removal can be performed by ion etching, particularly plasma ion etching, and the removal depth can be 0.2 μm to 2 μm. Partial removal or partial smoothing can be achieved by a resist mask that is applied prior to ion etching and that protects the coated area during the etching operation.

  2 and 3 show how the platinum thin film structure 10 conforms to the depth profile of the carrier. In this regard, FIG. 2 specifically shows that the shape of the profile in the depth direction is reflected in the shape of the platinum thin film structure 10. By this method, the profile in the depth direction is formed into a trapezoid. This avoids several steps (continuous profiling). The platinum thin film structure 10 follows a profile in the depth direction over the entire substrate with a substantially constant layer thickness.

  As shown in the plan view of FIG. 3, the conductor path 13 intersects the recess 17 in the lateral direction, that is, at an angle of 90 °. For example, other crossing angles are possible depending on the serpentine shape of the conductor track 13. The conductor track 13 can intersect the recess 17 at an angle in the range of 30 ° to 90 °.

  FIG. 2 further shows the layer structure on top of the platinum thin film structure. The first covering layer 14a is directly applied to the platinum thin film structure 13 and functions for passivation of the platinum thin film structure. The second coating layer 14b is applied to the first coating layer 14a and hermetically seals the first coating layer 14a.

FIG. 4 shows another embodiment of the present invention in which an intermediate layer 12 is disposed between the support and the platinum thin film structure 10. The intermediate layer 12 is also called an interface layer, and is formed from an electrically insulating metal oxide. This has the function of a buffer, absorbs the stress caused by the mismatch and transmits the stress at least partially inside the carrier. The intermediate layer 12 has a higher coefficient of thermal expansion than the ceramic support, in particular Al ₂ O ₃ , and it may be up to 50% higher than that of platinum. A magnesium oxide layer (MgO) applied by thin film technology and having a layer thickness of 0.2 μm to 3 μm has proven to be practical. Magnesium oxide has a thermal expansion coefficient of 13 × 10 ⁻⁶ / K. This coefficient of thermal expansion is greater than the coefficient of thermal expansion of Al ₂ O ₃ which is 6.5 × 10 ⁻⁶ / K and the coefficient of thermal expansion of platinum which is 9.1 × 10 ⁻⁶ / K. Instead of magnesium oxide (MgO), barium oxide (BaO) can be used for the intermediate layer 12. In order to set the thermal expansion coefficient of the intermediate layer 12, an electrically insulating metal oxide, for example, a mixture of magnesium oxide and Al ₂ O ₃ can be used. The thermal expansion coefficient of the intermediate layer 12 changes according to the content of Al ₂ O ₃ .

  Another embodiment in which the shape of one or more conductor tracks is varied is shown in FIGS. 5 and 6a-6d. The concept underlying this embodiment involves forming the conductor track 13 in a non-linear rather than linear fashion as shown in the upper part of FIG. 5 and in particular in a waveform as shown in the lower part of FIG. The corrugation extending in the horizontal direction, i.e. along the surface 11 of the carrier, has the effect that the linear expansion difference of the platinum thin film structure is separated into X and Y components. This separation has been found to have a positive effect on the stability of the platinum thin film structure in the presence of severe variable heat loads.

  The amplitude of the corrugated conductor path 13 is 0.2 × B to 2 × B, particularly 0.4 × B to 1 × B. The wavelength is 3 × B to 10 × B, in particular 4 × B to 7 × B. Here, “B” represents the width of the conductor path 13. It should be understood that the terms “amplitude” and “wavelength” have the same meaning as the variables commonly used for vibration. The amplitude corresponds to the peak value with respect to the zero line of the waveform. The wavelength corresponds to the oscillation period for the wave zero line as well. The zero line is the axis of symmetry in the wave length direction.

  As shown in FIG. 8, the conductor path 13 can have an upper meandering shape separately from the waveform of the conductor path 13. The meandering shape of the conductor path 13 constitutes an upper structure, and the waveform of the conductor path 13 is superimposed on this. In this regard, the waveform of the conductor track 13 constitutes the lower structure, which is provided at least in the conductor path portion between the meandering (upper structure) arcs. In addition, the meandering arc itself can be provided in the lower structure. The term “arc” should also be understood to mean a change in direction perpendicular to the conductor track, as shown in FIG. Also, the corrugated conductor path 13 can form electrode fingers arranged in a comb shape (shown in FIG. 8). In this case, the shape of the linear finger portion constitutes the upper structure, and the waveform as the lower structure is superimposed on this.

  6a to 6d show various shapes of the corrugations, which are shown in contrast to linear and wave-free conductor tracks, similar to FIG. For example, FIG. 6a shows that the conductor track 13 can have a sinusoidal waveform. A plurality of conductor paths 13 are arranged side by side in the same phase. FIG. 6b shows a wave-shaped conductor track 13 in which the wave is trapezoidal. Another example for waves is shown in FIG. In this example, the wave has a sawtooth shape. Here, the rectangular meandering shape can also be called a lower structure. The direction change of the conductor path 13 is performed at an angle of 90 °. FIG. 6d shows a mixture of the sine wave shown in FIG. 6a and the sawtooth wave shown in FIG. 6c. In this case, the side of the sawtooth wave is brought close to a sine wave shape and is rounded.

  FIG. 7 shows a further embodiment in which the first layer is improved by adding oxide nanoparticles. This has the effect that the volume of the first coating layer 14a changes with temperature change, and this reduces resistance drift. The first coating layer 14a is hermetically sealed with a second coating layer made of glass.

  The exemplary embodiments described above individually improve the dimensional stability of the platinum thin film structure 10, thereby counteracting resistance drift. Accordingly, each of these exemplary embodiments is disclosed independently. These exemplary embodiments can also be combined with each other, as illustrated with reference to the embodiment shown in FIG. Combining various exemplary embodiments leads to a synergistic effect, which is shown as a further reduction in resistance drift.

  Specifically, the first coating layer 14a made of oxide nanoparticles can be combined with all exemplary embodiments. This is because the passivation generally required by the platinum thin film structure 10 can be performed while improving the drift of the resistance value. As shown in FIG. 2, the first covering layer 14a is combined with a profile in the depth direction and a partially smoothed surface 11. As shown in FIG. 4, the first covering layer 14 a can be combined with the intermediate layer 12. Further, the intermediate layer 12 can be used together with the corrugated conductor path 13. Furthermore, the profile in the depth direction shown in FIG. 2 can be combined with the intermediate layer shown in FIG. 4, and can be combined with the corrugated conductor path 13 shown in FIG. 5, or shown in FIGS. 6a to 6d. It can also be combined with one of the waveforms. Combinations of all exemplary embodiments are possible.

  The carrier can be used to construct various sensors. For example, it is convenient to use the carrier for a temperature sensor having a platinum thin film structure. The use of a flow measuring sensor is possible as well, in which case the heating element and the temperature measuring element can be combined according to the principle of fluid measurement. An example of a further application of the present invention is shown in FIG. 8 in connection with a sensor module. This sensor module constitutes a multi-sensor platform and has a carrier substrate 23. The carrier substrate 23 can be modified according to one of the exemplary embodiments described above. For example, a strip-like depth profile (not shown) can be formed in the carrier substrate. The intermediate layer 12 is disposed on the carrier substrate 23 and functions as a buffer for the platinum thin film structure 10 disposed on the intermediate layer 12. The platinum thin film structure 10 can be a heater and / or sensor each having a contact connection. An insulating layer 20 is applied to the platinum structure 10 and an interdigital (interdigitated) electrode (IDE) structure 21 for conductivity measurement is disposed on the insulating layer. The interdigital electrode structure 21 is provided with an active functional layer 22. This is given by the customer, for example.

DESCRIPTION OF SYMBOLS 10 Thin film structure 11 Surface 12 Intermediate | middle layer 13 Conductor path 14a 1st coating layer 14b 2nd coating layer 15 Sliding part 16 Contact | adherence part 17 Recess 18 Side 19 Bottom surface 20 Insulating layer 21 Electrode structure 22 Functional layer 23 Carrier substrate

Claims (18)

A ceramic support, in particular an Al ₂ O ₃ support, on which a thin film structure (10) made of platinum or a platinum alloy is disposed,
The carrier and / or the thin film structure (10) is adapted to reduce mechanical stress due to different coefficients of thermal expansion;
a) the surface (11) of the carrier in the region of the thin film structure (10) is at least partially smoothed to reduce adhesion;
And / or b) the surface (11) of the carrier has an intermediate layer (12) on which the thin film structure (10) is disposed, and the thermal expansion coefficient of the intermediate layer (12) is 8 × 10 ^{-6 / K~16 × 10 -6 / K} , in particular ^{8.5 × 10 -6 / K~14 × 10} -6 / K,
And / or c) the thin film structure (10) has at least one conductor track (13), the conductor track (13) being at least partially corrugated and on the surface (11) of the carrier The amplitude of the corrugated conductor track (13) is 0.2 × B to 2 × B, in particular 0.4 × B to 1 × B, and the corrugated conductor track ( The wavelength of 13) is 3 × B to 10 × B, particularly 4 × B to 7 × B, where “B” is the width of the conductor path (13),
And / or d) a first coating layer (14a) comprising oxide nanoparticles, in particular Al ₂ O ₃ and / or MgO oxide nanoparticles, is applied directly to the thin film structure (10). A carrier characterized by.   The surface (11) in the region of the thin-film structure (10) forms at least one sliding part (15) and at least one tight contact part (16), according to claim 1, The carrier described.   The carrier according to claim 1, characterized in that the surface (11) in the entire region of the thin-film structure (10) is smoothed.   The surface (11) in the region of the thin film structure (10) has a profile in the depth direction that forms at least one recess, in particular, a belt-like depth profile that forms at least one recess. The carrier according to any one of claims 1 to 3, characterized in that the surface (11) of the recess (17) is smoothed.   The at least one conductor path (13) of the thin film structure (10) is arranged at an angle in a range of 30 ° to 90 ° with respect to the profile in the depth direction of the belt, The carrier according to claim 4.   The recess (17) has a trapezoidal cross section with two inclined side faces (18) and a bottom face (19) between the side faces (18), and at least one side face (18), in particular both side faces (18). The carrier according to any one of claims 4 and 5, characterized in that it stands up at an angle of 10 ° to 80 °, in particular 45 ° to 60 °, with respect to the bottom surface (19).   The recess (17) is 0.4 μm to 1.2 μm, in particular 0.6 μm to 1.0 μm deep and / or 5 μm to 20 μm, in particular 10 μm to 15 μm wide. The carrier according to any one of claims 4 to 6.   The strip-shaped profile in the depth direction has a plurality of parallel recesses (17), and the interval between the recesses (17) is 5 μm to 20 μm, particularly 10 μm to 15 μm. Item 8. The carrier according to any one of Items 4 to 7.   9. The thermal expansion coefficient of the intermediate layer (12) is at most 1.5 times greater than the thermal expansion coefficient of the thin film structure (10), according to claim 1. Carrier.   10. The carrier according to claim 1, wherein the intermediate layer has a thickness of 0.2 μm to 3 μm, in particular 1 μm to 2.2 μm.   The carrier according to any one of claims 1 to 10, wherein the intermediate layer (12) comprises at least one electrically insulating metal oxide. The intermediate layer (12) contains MgO and / or BaO, in particular consists of MgO and / or BaO, or contains a mixture of at least one electrically insulating metal oxide and Al ₂ O ₃ or from the mixture The carrier according to any one of claims 1 to 11, characterized in that   The corrugated conductor track (13) has a plurality of arcs extending along the surface (11), and the corrugated lower structure is formed at least in a portion of the conductor track between the arcs. Or the corrugated conductor path (13) forms a plurality of finger-like parts of an electrode arranged in a comb shape. The carrier described.   14. A carrier according to any one of the preceding claims, characterized in that the corrugated conductor track (13) is in the form of a sine wave and / or a sawtooth wave and / or a trapezoidal wave. .   15. The carrier according to claim 1, wherein the first coating layer (14a) is hermetically sealed with a second coating layer (14b) made of glass in particular. .   A sensor element, a heating element or a sensor module comprising the carrier according to any one of claims 1 to 15.   Various sensor structures are arranged on the carrier, the thin film structure (10) made of platinum or a platinum alloy forms at least one sensor structure, and at least one electrode structure. The sensor module according to claim 16, wherein another sensor structure is formed. A method for producing a ceramic carrier according to claim 1, comprising:
At least in the region of the thin film structure (10), the surface (11) of the carrier is removed for smoothing by etching, in particular ion etching, and / or the intermediate layer (12) is thin film, in particular PVD or Applying to the surface (11) of the carrier by a CVD method and / or applying a corrugated conductor track (13) to the surface (11) of the carrier by a thin film method, in particular a PVD method or a CVD method or a lithography method, Method.

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